Marker-Assisted Introgression of Terminal Heat Tolerance and High-Zinc Quantitative Trait Loci (QTLs) in Bread Wheat (Triticum aestivum L.) for Climate-Resilient Nutritional Security

Abstract

Terminal heat stress during the grain-filling stage and widespread micronutrient (especially zinc) deficiency poses major threats to global wheat productivity and nutritional security. This study focuses on the marker-assisted introgression of QTLs conferring terminal heat tolerance (early anthesis via Xbarc186 on 4AL, kernel weight via Xgwm190 on 1BS) and high grain zinc concentration (including Gpc-B1/NAM-B1 on 6BS and stable QTLs on 4DS, 6AS, and 7BL) into elite bread wheat backgrounds using marker-assisted backcross breeding (MABB). Foreground selection with tightly linked SSR/SNP/KASP markers, recombinant selection to minimize linkage drag, and background selection for high recurrent parent genome recovery (90–98%) enabled the development of improved lines with enhanced heat resilience and elevated grain zinc (target >45 mg/kg) without compromising yield potential. Physiological mechanisms such as maintained photosynthetic efficiency, antioxidant defense, stay-green trait, and efficient nutrient remobilization underpin the tolerance, while biofortification leverages wild emmer and synthetic hexaploid diversity. Multi-environment evaluations confirm significant improvements in thousand-grain weight, yield stability under late-sown conditions, and grain zinc content. Integration with speed breeding and genomic selection accelerates the development of climate-resilient, nutritionally enriched wheat varieties, offering a sustainable pathway to combat hidden hunger and ensure food security in heat-prone regions.